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Chemistry > C4 - the periodic table > Flashcards

C4 - the periodic table Flashcards

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0
Q

What are the charges and relative masses of an electron, proton and neutron?

A

Electron: C = -1 RM = zero

Proton: C = +1 RM = 1

Neutron: C = 0 RM = 1

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1
Q

What is the nucleus of an atom made up of?

A

Protons and neutrons.

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2
Q

How to calculate the number of protons, electrons and neutrons of an atom?

A

E.g sodium
mass number = 23
atomic number = 11

Atomic number = number of protons = number of electrons

Number of neutrons = mass number - atomic number

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3
Q

What is an isotope?

A

Elements with the same atomic number but different mass numbers.

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4
Q

How are elements arranged in the periodic table?

A
  • Elements in the same group (with the same number of electrons in the outer shell) are arranged vertically.
  • Elements in the same period (in order of how many shells the electrons occupy) are arranged horizontally.
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5
Q

Which scientists developed atomic theory?

A

An early theory of atoms was developed by John Dalton. His explanation was provisional, but later was confirmed by better evidence. When J.J. Thompson, Rutherford and Bohr found new evidence, their explanations changed the model of the atom. With later evidence their predictions were confirmed.

Ideas can change rapidly following unexpected results. Geiger and Marsden had some unexpected results which made significant contributions to Rutherford and Bohr’s ideas.

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6
Q

Why do atoms form bonds?

A

Atoms with an outer shell of eight electrons have a stable electronic structure. Atoms can be made stable by transferring electrons, this is called ionic bonding.

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7
Q

What happens to metal atoms during ionic bonding?

A

Metal atoms lose electrons to get a stable electronic structure. If an atom loses electrons, a positive ion is formed, as there are fewer negatively charged electrons than the number of positively charged protons in the nucleus.

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8
Q

What happens to non-metal atoms doing ionic bonding?

A

Non-metal atoms gain electrons to get a stable electronic structure. If an atom gains electrons a negative ion is formed. This is because there will be more negatively charged electrons in the number of positively charged protons in the nucleus.

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9
Q

What are positive and negative ions held together by?

A

Electrostatic attraction.

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10
Q

What happens during the bonding of magnesium oxide?

A
  • magnesium atoms lose two elections to form positive magnesium ions.
  • oxygen atoms gain two elections to form negative oxide ions
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11
Q

What happened during the bonding of sodium oxide?

A
  • a sodium atom only has one electron to lose to make a sodium ion, but an oxygen atom needs to gain two elections to make an oxide ion
  • two sodium atoms are needed to provide the two elections needed, so two sodium ions are formed for every one oxide ion
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12
Q

Describe the structure of sodium chloride or magnesium oxide.

A

The structure of sodium chloride or magnesium oxide is a giant ionic lattice, in which positive ions have strong electrostatic attracting to negative ions. They always exist as doors.

Sodium chloride solution can conduct electricity.

Sodium chloride and magnesium oxide conduct electricity when they are molten.

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13
Q

What do the physical properties of sodium chloride and magnesium oxide mean?

A
  • they have high melting points as there are strong attractions between positive and negative ions.
  • they do not conduct electricity when solid because the ions cannot move.
  • they conduct electricity when in solution or as a molten liquid as the ions are free to move.
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14
Q

Why is the melting point of MgO higher than NaCl?

A
  • there are Mg 2+, not Na+ ions and O2-, not Cl- ions, so there are stronger electrostatic attractions between positive and negative ions.
  • each Mg atom donates two electrons to the oxygen atom, which makes a stronger bond when sodium atoms transfer one electron to chlorine atoms.
  • magnesium ions are very small in radius, so magnesium can get much closer to oxygen, which makes the bond stronger. More energy is needed to separate these ions.
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15
Q

What is covalent bonding?

A

When non-metals share electron pairs between atoms.

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16
Q

What is the group number of an element?

A

The group number is the same as the number of electrons in the outer shell.

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17
Q

Explain the development of the periodic table.

A
  • In 1865 Newlands put 56 elements into groups and saw that every eight element behaved similarly. This was not accepted for 50 years until other scientists discovered more evidence.
  • In 1869 Mendeleev arranged the elements in order in a table. He noticed periodic changes in properties. He saw there were gaps in his pattern and predicted new elements would be found.
  • In 1891 Mendeleev’s table still did not contain the noble gases. Later investigations confirmed his idea of periodicity and his predictions on the discovery of missing elements.
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18
Q

Explain the properties of group 1 elements (alkali metals).

A

Caesium and rubidium are both group 1 metals and so have similar properties to lithium, sodium and potassium:

  • they react vigorously with water.
  • hydrogen gas is given off.
  • the metal reacts with water to form an alkali (the hydroxide of the metal).
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19
Q

Explain the reactivity patterns of group one alkali metals

A

Atoms of group one alkali metals have similar properties because they have one electron in their outer shell.

Atoms of alkali metals react, losing electron and forming:

  • a full outer shell, to create a stable electronic structure
  • an ion, which has one more positive charge in its nucleus than negative electrons in its shells, so it becomes a positive ion.

This can be represented by the equation:

Na+ - e- –> Na+

20
Q

What makes an atom reactive?

A

The easier it is for an atom of an alkali metal to lose one electron, the more reactive it is.

21
Q

How do you carry out a flame test to find out if lithium, sodium or potassium is present in a compound?

A

The test is carried out whilst wearing goggles.

  • a flame-test wire is moistened with dilute hydrochloric acid.
  • the flame-test wire is dipped into the solid chemical.
  • the flame-test wire is put in a blue Bunsen burner flame
  • the colours of the flame are recorded
22
Q

What colours do some alkali metals go in a flame?

A

lithium - red
sodium - yellow
potassium - lilac

23
Q

At room temperature what state and colour is chlorine, bromine and iodine?

A

At room temperature, chlorine is a green gas, bromine is an orange liquid and iodine is a great solid.

24
Q

What happens to halogens when they react?

A

Halogens have similar properties because when they react each atom gains one electron to form a negative ion with a stable electronic structure.

25
Q

Why does the atomic radii affect the reactivity of halogens?

A

The neared the outer shell is to the nucleus; the easier it is for an atom to gain one electron. The easier it is to gain the electron, the more reactive the halogen.

26
Q

What happens when a halogen reacts with an alkali metal? And the equation?

A

When halogens react with alkali metals, a metal halide is made.

Potassium + iodine –> potassium iodide

2K + I2 –> 2KI

27
Q

Tell me about displacement reactions of halogens.

A

If halogens are bubbled through solutions of metal halides there are two possible outcomes: no reaction or a displacement reaction.

28
Q

Word and symbol equation for the displacement reaction between chlorine and bromide?

A

Chlorine + potassium bromide –> potassium chloride + bromine (orange solution)

Cl2 + 2KBr –> 2KCl + Br2

29
Q

How is the trend in reactivity shown in halogens?

A

The trend in reactivity is shown by displacement reactions. The reactivity of the halogens increases further up the group. Knowing this trend allows the reactions between halogens and metal halides to be predicted.

30
Q

What are coloured compounds?

A

Compounds that contain a transition element are often coloured.

  • copper compounds are often blue.
  • iron(II) compounds are often pale green.
  • iron(III) compounds are often orange/brown
31
Q

What are transition elements and their compounds often used as?

A

Catalysts.

32
Q

What happens to a transition metal carbonate when heated?

A

It undergoes thermal decomposition to form a metal oxide and carbon dioxide.

On hearing:
FeCO3 decomposes forming iron oxide and carbon dioxide.
CuCO3 decomposes forming copper oxide and carbon dioxide.

33
Q

Balanced symbol equations for the thermal decomposition of transition metal carbonates.

A

CuCO3 –> CuO + CO2

FeCO3 –> FeO + CO2

MnCO3 –> MnO + CO2

ZnCO3 –> ZnO + CO2

34
Q

What are metal hydroxide ppts?

A

When sodium hydroxide solution reacts with compounds of each transition metal to make a solid of a particular colour. The addition of sodium hydroxide solution identifies the presence of the transition metal ions in solution.

  • Cu2+ ions form a BLUE SOLID
  • Fe2+ ions form a GREY/GREEN SOLID
  • Fe3+ ions form an ORANGE/BROWN GELATINOUS SOLID
35
Q

What are the balanced symbol equations for the ppt reaction of sodium hydroxide reacting with the compounds of each transition metal?

A

Cu2+ + 2OH- –> Cu(OH)2

Fe2+ + 2OH- –> Fe(OH)2

Fe3+ + 3OH- –> Fe(OH)3

36
Q

What is an example of a physical property of a metal?

A

The high thermal conductivity of copper.

37
Q

What is an example of a chemical property of a metal?

A

Resistance to attack by oxygen or acids shown by gold.

38
Q

Why do metals have high melting points and high boiling points?

A

Due to their strong metallic bonds.

Metals often have high melting points and boiling points, because a lot of energy is needed to overcome strong attractions between delocalised electrons and close-packed positive metal ions.

39
Q

What is a metallic bond?

A

A metallic bond is a strong electrostatic force of attraction between close-packed positive metal ions and a ‘sea’ of delocalised electrons.

40
Q

What are superconductors and give some examples

A

Superconductors are materials that conduct electricity with little or no resistance.

The electrical resistance of mercury suddenly drops to zero at -268.8 • C

41
Q

What happens when a substance goes from its normal state to a super conducting state and it no longer has any magnetic fields inside it?

A
  • if a small magnet is brought near the superconductor, it is repelled.
  • if a small permanent magnet is placed above the superconductor, it levitates.
42
Q

What ads the benefits of superconductors?

A
  • loss free power transmission
  • super fast electronic circuits
  • powerful electromagnets
43
Q

What’re the difficulties with superconductors?

A
  • they work only at v low temperatures; this limits their use
  • superconductors that function at 20 degrees C need to be developed
44
Q

What’re the three main stages of water purification?

A
  • sedimentation -chemicals are added to make solid particles and bacteria settle out
  • filtration of very fine particles -a layer of sand on gravel filters out the remaining fine particles; some types of sand filter also remove microbes
  • chlorination -chlorine is added to kill microbes
45
Q

What is distillation?

A

A separating technique. Distillation takes huge amounts of energy so ta very expensive and only used when there is no fresh water.

46
Q

What is a ppt reaction?

A

Where two solutions react to form a chemical that does not dissolve.

47
Q

Precipitation reactions between barium chloride and magnesium sulfate

And silver nitrate and halogen halides

A

Barium chloride + magnesium sulfate –> barium sulfate (white ppt) + magnesium chloride

Silver nitrate + sodium bromide –> silver bromide (cream ppt) + sodium nitrate

Silver nitrate + sodium iodide –> silver iodide (yellow ppt) + sodium nitrate

Silver nitrate + sodium chloride –> silver chloride (white ppt) + sodium nitrate

BaCl2 + MgSO4 –> BaSO4 + MgCl2

AgNO3 + NaBr –> AgBr + NaNO3

AgNO3 + Nal –> AgI + NaNO3

AgNO3 + NaCl –> AgCl + NaNO3

Chemistry (6 decks)

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